By the way, defining more than two ways on a tile (a multi-bridge) is kinda unnecessary and that's way I wouldn't bother with so many tiles/permissions but just mark some specific tiles as bride tiles which have a flag if the player is standing on or under them. NPCs generally just on bridges and finding items dependent on where the player is.
Did I mentioned interfaces? ... Oh yeah, I did.
If you have interest, I can give you the code for my mapper, even if it's just an unfinished rebuilt of the RPG-Maker.